Open Source, Delay Tolerant Network, Internet of Things

Knowledge Without Boundary

Saturday, December 13, 2014

Figure 4.5 shows offline email system
network protocol layout. When email is sent, a message was sent from the sender
mail server Mail Transport Agent (MTA). Both MTA side communicates using Simple
Mail Transfer Protocol (SMTP) Server. The recipient MTA delivers the email to
the Mail Delivery Agent (MDA) which stores the email as it wait for the user to
accept it. Internet Message Access Protocol (IMAP) used for retrieving email on
MDA.

MDA is protected by login system
where it needs a username and password. Email is retrieved by using Mail User
Agent (MUA) where it is called an email client on the user device. Webmail is
used for this thesis work. If the email destination is not in the local
network, the email delivery is pending and the data remain in the mail server
storage until it is transferred to the infomediary device. This operation
matches the bundle protocol (BP) where the data being stored temporarily and
later forwarded to next destination. When the infomediary device establishes a
network connection with the offline mail server, the mail database synchronization
application will transfer the email data from offline mail server to infomediary
device and retrieve new email data from infomediary device to the offline mail
server. The new email data from infomediary device which is received from online
mail server will be in the new pending email delivery where it is being sent
immediately since the destination was in the network until it reaches the user
to accept it. The Dynamic Host Configuration Protocol (DHCP) is a network
protocol used to configure devices that are connected to a network. The SSID
and security codes for the access points are chosen by the administrators. This
offline email system used static IP addresses. Both the online and offline server
computers are configured as DHCP servers. This enables the servers to allocate
IP addresses to any DHCP client.

Figure 4.6 shows online email system
network protocol layout. The process is the same as when the infomediary device
establishes a network connection with online mail server, the mail database synchronization
application will retrieve email data from infomediary device to online mail
server and transfer the new email data from online mail server to the infomediary
device to be sent to the offline mail server. The email data from infomediary device
which is received from the offline mail server will be in pending delivery
where the delivery is executed immediately because of the destination is
available in the network until it reaches the user to accept it.

Friday, December 12, 2014

Figure 4.3
shows the flow of the email in the networking protocol. This email queue delay
period was set by the email system administrator. It can be set to minimum
value 0 and maximum value is 2147483647 due to maximum value for a 32-bit
signed integer (int32) supported by a SQL database. This means that the email
data can be kept in temporary storage for a maximum period of 2147483647
minutes equal to 4083 years. The user at the offline server will write and send
an email at application stage where the email data will be stored in the
offline mail server for a maximum period of 4083 years before it being
discarded. If the offline or online email server computer was shutdown or
restart, the pending email remains in the database and will eventually discard
when the time delay exceeded. Once the offline mail server connected to infomediary
device, the pending email data will move through TCP in Transport layer where
the application use NetBIOS over TCP/IP (NBT) to request NetBIOS name server to
send an IP address of the destination NetBIOS at infomediary device [20]. Link layer builds
an ethernet frame and pass it to the network operating system to be sent to the
NetBIOS name server. The NetBIOS name server sends back the NetBIOS name. After
the TCP connection is established, the application transfers the file to the
target host which is infomediary device.

On the other
side, when infomediary device establishes a connection with an online mail server
computer, the email data is transferred to the mail server database. The data are
transferred packet by packet and when the last packet arrives, the files are
reassembled and completed files passed to the application layer. Figure 4.4
shows the Store and forward operation between mail server A, infomediary device
and mail server B. Each node contains storage to store the email data.

Thursday, December 11, 2014

Firefox OS, also known as Boot to Gecko is a Linux kernel-based open-source operating system for smartphones and tablet computers and is set to be used on smart TVs. It is being developed by Mozilla, the non-profit organization best known for the Firefox web browser.

Firefox OS is designed to provide a complete community-based alternative system for mobile devices, using open standards and approaches such as HTML5 applications, JavaScript, a robust privilege model, open web APIs to communicate directly with cellphone hardware, and application marketplace. As such, it competes with commercially developed operating systems such as Apple's iOS, Google's Android, Microsoft's Windows Phone and Jolla's Sailfish OS as well as other community-based open source systems such as Ubuntu Touch.

Firefox OS Simulator is a test environment for Firefox OS. Use it to test your apps in a Firefox OS-like environment that looks and feels like a mobile phone. After installing it, go to Web Developer > Firefox OS Simulator to access its features. From your Firefox Browser, go here to install the addon:

Reicast team are looking for testers to test their latest dreamcast emulator release candidate before release to the Play Store. Reicast is a Dreamcast emulator for Android.

We're looking for some brave souls to test the latest rc, before it gets rolled out to the play store. If you know how to install 3rd party apks, please join the fun and report breakage~

Let's release current master as r7Version: r7-rc1-22e95deApk: http://reicast-builds.s3.amazonaws.com/builds/heads/master-22e95de/reicast-android-debug-22e95de.apkSource: https://github.com/reicast/reicast-emulator/releases/tag/r7-rc1(Will be updated as needed)In case you have issues, please note which version you tried. Otherwise we can't help.Unless there are any serious objections, I'll build and upload tonight to Google Play, reicast site, ouya & amazon stores. -> +1 day to get some more feedback (11/12)

Figure 4.2 shows the offline email system architecture. Each Wi-Fi access point uses a star topology. Each node connected by using a mobility device which is called infomediary device. There is only one online mail server needed and offline mail server can be more than one for each rural village. Offline mail server and online mail server have the same required software installed which is Uniform Server, hMailServer, roundcube and FreeFilesync. Infomediary device has Samba File sharing installed to enable the data transfer from each node. Online mail server configured to be able to connect to the internet and accessible from the internet. This is the transit point for this offline email system to be able to send or receive email from internet email such as Gmail, Hotmail etc.

This offline email system is using TM Streamyx Dynamic 1 MBps Internet Service Provider (ISP) with conjunction with DtDNS service. Dynamic IP is used by Internet Service Provider (ISP) so that one external IP address can be assigned to several users. ISP's use Sticky Dynamic IP Addressing and do not change the external IP address very often and only change the external IP address as ISP deem it necessary. DtDNS service used to enable the system to be accessible from the internet without worrying about frequently change of external IP address.

Wednesday, December 10, 2014

There are several of the
DTN Email system exists such as Bytewalla
5, DTNmailex and offline Gmail. Mail client for this
thesis offline email system, Bytewalla 5
and offline Gmail is a web based.
User can use a web browser to access the webmail. There are two mail servers
for the offline email system which is an offline local mail server and an online
local mail server. Bytewalla 5 also
has two mail servers which are offline DTN mail server and online DTN mail
server while there is only internet mail server available for offline Gmail.

DTN
implementation of this offline email system is based on TCP/IP. The advantage
of this approach is the user can use the offline email system as it was a
normal email system and may not even noticed it was a DTN email system. The Bytewalla 5 uses a native DTN
implementation designed by Delay Tolerant Networking Research Group (DTNRG)
while offline Gmail uses Google Gears.

This offline
email system use Windows operating system for its web server, mail server
application and database synchronization application. Bytewalla 5 uses Ubuntu 8.04 LTS a Linux operating system for its
DTN mail server and offline Gmail is
browser based where it use Google mail server.

Data mule for
being used is an android phone where it acts as an infomediary device. The Samba File sharing application is used
to enable a network storage connection with a mail server where it receives an
email data from database synchronization software to be sent to the destination
mail server. Bytewalla 5 also use
android phone as a data mule. It has three main applications running which is
DTNService for handling DTN communication, DTN Manager to configure, monitor
and manage DTNService and DTNApps (DTNSend for sending messages and DTNReceive
for receiving messages). Offline Gmail
use Web Browser with Google Gears to
store some online files to be used offline.

Temporary
storage location for a pending email data in this offline email system and Bytewalla 5 is stored in email server
computer while offline Gmail storage
is in the mail client computer. Endpoint ID for this offline email system and offline Gmail is a standard email
address where there is a local part, @ sign, and domain part. As an example:
test1@email.com. [19]. Table 4.2 shows a
comparison of this thesis project offline email system with Bytewalla 5 and offline Gmail.

Table 4.3 shows
the comparison of selected free web server Uniserver
7.1.4 and XAMPP 1.8.1. Both web servers
offer the same feature for a setting up a Windows home server. Uniserver has been selected because it
has a Cron feature which can be used with DtDNS service. Cron is a job
scheduler allowing scripts to be run automatically at a certain time or date.
It is used to update the external IP address of the server computer to the
DtDNS service.

Table 4.6 shows
comparison of File Synchronize software for FreeFilesync,
Synchronize It and rsync. FreeFilesync is selected for this thesis project because of it a
free Open Source for Windows and support for batch file for automated file synchronization.